12 Intermittent Fasting Tips for Athletes

Yesterday, I explained the potential benefits and drawbacks of intermittent fasting for athletes. Maybe yesterday’s post intrigued you. Maybe you’re curious about this whole intermittent fasting thing but don’t want to sacrifice your performance in the gym or on the field.

What are my specific recommendations for athletes who wish to explore intermittent fasting? I’ve got twelve…plus some details about my own fasting and workout routine.

1) Use Restricted Eating Windows Over All-day Fasts

Athletes who want to lean out or maintain strength and performance while lowering body weight might have more success with shortened eating windows than with all day fasts or “one meal a day.” Fast for 12-16 hours, train, and break the fast. Then have 8-12 hours to eat. This will give you a nice block of almost pure fat-burning with enough of an eating window to get the calories you need to grow and maintain muscle and to recover from your training.

2) Small Amount Of Protein Pre-workout May Help

Having a small bit of protein (20 grams whey or maybe 10 grams BCAAs) can help if truly fasted workouts are too hard.

3) Fasted Walks In the Mornings

Whether you skip breakfast or dinner, you’ll have a block of time in the mornings before eating anything. That’s when fat-burning will be upregulated, and brisk fasted walking is a nice way to enhance it.

4) Light Cardio After a Fasted Lifting Session

A heavy lifting session will get free fatty acids liberated from your adipose tissue, particularly if you’re fasted. Doing some very light cardio after your weights should in theory help you utilize all that mobilized adipose tissue. Go for a 20-minute walk, do ten minutes on the bike, or something similar.

5) “Train Fasted, Race Fed”

This is a more intense version of “train low-carb, race high-carb,” a popular and well-researched method of enhancing fat adaptation and increasing fuel efficiency in endurance athletes. Training in a fasted state “forces” the athlete to burn stored fat because, well, there isn’t a whole lot of carbohydrate available. Plus, fasting necessarily increases the circulation of free fatty acids, which can be burned for fuel. This applies to everyone, not just people “racing.” The trick is to train in a fasted state (if you find it helps) and compete (whether it’s CrossFit games, a basketball game, a lifting competition, etc.) in a fed state—as long as it seems to improve your performance.

6) Most Of the Time, Break the Fast Shortly After the Workout

If you’re skipping dinner and eating breakfast, try morning workouts. If you’re skipping breakfast and eating lunch, try afternoon workouts.

7) Every So Often, Continue the Fast After a Workout

This enhances secretion of growth hormone, which fasting already elevates. Don’t make this an every-workout habit, though. Diminishing returns and all.

8) Every Athlete Can Probably Benefit From the Occasional Longer Fast (24 hours+)

This will normalize inflammation, boost growth hormone, and upregulate autophagy, giving you all the necessary co-factors for rest and recovery. Tissues will heal, joints will recover. Do nothing more on these days than easy movement (walks, hikes, bike rides, swims). Time this fast away from competition because your performance may suffer. Do these once a week or every other week.

9) If You Have Joint Problems (or Want To Avoid Them), Take Collagen or Drink Bone Broth Before a Fasted Workout

Fifteen grams of pre-workout collagen or gelatin with a few hundred milligrams of vitamin C has been shown to improve collagen synthesis in connective tissue, and collagen shouldn’t disrupt the fast too much.

10) More Isn’t Better

I see this a lot, especially with endurance athletes who get into intermittent fasting. They start eating breakfast later and see their times drop and their body fat disappear. They feel lighter on their feet, faster, just better all around. So they push breakfast even later and maintain the benefits, even building on them. Pretty soon they’re skipping lunch, and their performance drops off a cliff. When trying to use fasting to improve athletic performance, less is more generally speaking.

11) Realize That Exercise and Fasting Are Additive

For the average couch potato to get the benefits of fasting, he or she might need to go 16 hours without food. The couch potato isn’t liberating body fat through training. The couch potato isn’t getting into ketosis through physical activity. The couch potato isn’t increasing mitochondrial density—the power plants of the cells which actually process fuel—with exercise. The athlete is doing all those things. For the athlete, many of the benefits of fasting will appear with smaller fasting windows.

12) Consider Sleeping Low

Sleeping low” is an alternative to full-on fasting that actually seems to work well. This is how you do it:

  • Afternoon workout. This should be something intense that depletes glycogen—sprinting, metabolic conditioning, high volume strength training, high intensity endurance workouts.
  • Eat protein and fat at dinner, no carbs. You’re not refilling your glycogen. You’re reveling in your lack of glycogen.
  • Sleep.
  • Wake up and do low-intensity cardio (walking, cycling, hiking, swimming) before breakfast. Eat carbs at breakfast.
  • Repeat.

When a group of triathletes followed this protocol, both their submaximal efficiency and supramaximal capacity. High submaximal efficiency means you get more power out of each stroke/pedal/step with less energy required. Your “easy pace” becomes faster and more powerful. High supramaximal capacity means you can last longer at your maximum power output.

It’s likely that full-on fasting could be integrated into this protocol. Maybe with a compressed eating window leading up to the afternoon workout.

A Few Words About My Routine:

A few people have asked, so I’ll give an overview of how I approach this topic for myself:

Every day, I do time-restricted feeding. This isn’t a formal declaration I make with myself every day. It’s not really a schedule. It just happens naturally. I wake up and most days I’m not very hungry for anything but a cup of coffee, so I “skip” breakfast and eat my first meal around one in the afternoon following a workout.

Most of my workouts are performed in a fasted state, and I usually keep fasting after the workout for a few hours. I’ll extend that fast after the workout to really take advantage of the increased secretion of growth hormone. I’m not really trying to “get big” or anything, I’m more interested in maintaining body comp and function and increasing longevity. Natural pulses in growth hormone help with that.

Before most workouts, I’ll do some Collagen Fuel. This doesn’t seem to impair my fast and it helps me keep my joints working well—an important part of aging.

Half an hour before my weekly Ultimate Frisbee game, I’ll also include a little Primal Fuel (my whey isolate powder). This just helps me perform better. I’m not going to lose. (By the way, I’ll talk more about protein types for different functions in an upcoming post.)

That’s it for today, folks. Have you tried any of these fasting workout tips? Have they worked? Do you have any more to add? Let us know down below!


Marquet LA, Brisswalter J, Louis J, et al. Enhanced Endurance Performance by Periodization of Carbohydrate Intake: “Sleep Low” Strategy. Med Sci Sports Exerc. 2016;48(4):663-72.

TAGS:  calories

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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22 thoughts on “12 Intermittent Fasting Tips for Athletes”

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  1. What fasting schedule do you recommend for those who work out early in the morning (between 5am and 7am?)

    1. I get around 4am, so some light stretching, drin some green ta, and then go surf for a couple hours or more. On alternate days I do sprints or planking, pull ups and pushups after my surf.

      My eating window is 10am-ish to 6pm-ish.

      I’m 53 years old and have been surfing for 33 years. I love fasted workouts and I’m not really hungry until a couple hours or so after exercise.

      1. Hi Clay,

        Unrelated to fasting, but can I ask — where do you live? The idea of surfing every day just sounds dreamy. Are you happy with your spot? Could you give a little “top 5” cities/surf communities for everyday surfers? Thanks!

    2. I’m curious about this too. I get up at 5.30am to lift weights most days. I always have coffee with creatine before the gym and feel amazing on this. Usually have it black, sometimes with a splash of unsweetened almond milk. Sometimes I add collagen too and think I might start doing that daily. I have tried the ketogains suggestion of having a bit of whey protein before the gym (similar amount to what Mark mentioned) the theory being it gets digested and ready for your muscles to use exactly when they need it at the end of your workout. I sometimes feel a bit too full if I have the whey though. I’m thinking of trying stopping eating earlier in the evening, say 6pm or 7pm, which will be good for me because evening is when I tend to snack on way more nuts/cheese/olives than I should, and have breakfast after I get back from the gym (around 7.15am) or when I get to work about 9am. So a 12 to 15 hour fasting period overnight.

  2. Great post. I’m a 46yo afternoon workout guy (4:00). The goal is lean mass and fat reduction. Taking what you’ve posted…I would shut down the feed trough at 8:00. Skip breakfast and eat about noon. Workout at 4 but hold off for a bit before post workout feeding. Mix in a total fast occasionally. Ideally I would workout fasted but afternoon work outs makes that difficult. Sound about right?

  3. Thanks Mark – I need to get back to IF again. I’ve never tried a 24hr fast before, but I might have to give it a try.

    Also – thanks for the heads up on Ultimate. I found a Tuesday pickup game and started going about a month ago. I’m getting a good sprint/change of direction, have a fun time workout, but I’m 52 and found a lot of aches and pains I had forgotten about.

    Wed has become my ‘rest’ day.

  4. I hear what you’re saying re fasted resistance training and growth hormone Mark – but how do you square that with the view of experienced trainers such as Martin (Leangains) Berkhan and Luis (Ketogains) Villasenor who recommend NEVER training without first ingesting whey/ essential aminos? Otherwise the training effect itself will be highly catabolic plus you are about to end the fast anyway so why not have some protein just before your workout?

    1. I think bodybuilders worry too much about catabolism, that’s how you end up with the 8 meal a day types that get up at 4 am to drink a protein shake 😉 I’ve read most of what Martin Berkhan wrote but can’t quite remember him saying that you should NEVER train fasted, where did you read that?

      Assume you train 60 minutes, does 60 minutes without protein really make that much of a difference with protein synthesis? Do 240? And does the growth hormone perhaps help mitigate that by causing a greater anabolic response later on?

  5. Hi Mark, I’m a 60 yo female and I’ve been trying to figure out the best way to IF with 3 days per week double (AM and PM) workouts, 3 days per week single (PM) workouts and 1 recovery day. My sports are Crossfit, Olympic lifting, strength training, and running. Any thoughts on how to dial this in without losing strength and/or power during workouts would be greatly appreciated. Absolutely believe in the power of IF and wish to take advantage of it as I continue to age gracefully. Thanks so much for all the great information you share!

  6. Hello!

    How can I have and interview mith Mr Mark and ask him if I’ve been doing things in the good and correct way?

  7. Can you use creamer in Coffee during workout? If you are in a faster state?

  8. I appreciate these informative blogs.

    I’m wondering if you might answer either me directly or in a blog how to handle sugar alcohols when tracking carbohydrates. I bake a lot of goodies using Lakanto powdered monk fruit sweetener with Erythritol. I know to substitute Fiber for net carbs yet I’m unclear what your position is about sugar alcohols. (Please point me in the right direction should I be missing earlier explanations!)

    Thank You!

  9. Mark,
    When you take collagen fuel prior to your fasted workout you say it “doesn’t seem to impair my fast.” How do you know this? Is this a subjective judgement or have you done specific lab tests to confirm this or is it based off of studies you’ve read? Genuinely curious.

  10. Hi All,

    Anyone suffer from sleeplessness during fasting days? This has come out of nowhere for me and is now a regular occurrence.

    1. I’m on a longer fast now (48h in) and I barely sleep, maybe 4 hours a night. I haven’t been a great sleeper before, but this can be somewhat worrying. From what I hear it’s not uncommon.

  11. l am 30 years old. I usually get around 5.30am and begin each day with a morning jog . Always l have some low-protein food and cereals for breakfast.My eating window is 8am-ish to 6pm-ish.Most of my workouts are performed in a fasted state, and l usually play badminton after dinner. Most importantly
    never eat at ninght.Besides,yoga is my bedside routine.Remember to have a good sleep at the end!

  12. Am I to assume that taking BCAA’s during my fasted workout will not break the fast? I have hear to the contrary but I trust your opinion.

  13. Great article Mark. Ive been intermittent fasting for a couple weeks now and at first it took my body some time to adjust in the gym. Wish I had come across this article before starting, that’s for sure.

    I’ve been hearing a lot about the potential benefits of implementing CBD oil into my workout and from what I’ve gathered there are a lot of benefits to it. There’s a good article on it here: https://www.healthyfitholistic.com/cbd-for-athletes/. Just wondering if you knew anything about it or had heard about it from friends.

  14. Can you speak to coffee? I keep reading different answers to the question of whether coffee breaks the fast. I too often don’t eat until 1 or 2 or 4pm, but I do drink coffee all morning, about 15 of them per day, each with a small quantity of full-fat milk. I don’t like the taste of cream and find bulletproof-type coffees undrinkable.

    I’m not going to stop drinking coffee, but I would love to know whether I need to stop claiming I’m doing IF. Thank you!

  15. While working out you need to have carbs and you will and can train much harder and make more muscle. When I do this for 12 weeks after not doing carbs before, I get a slingshot and make 10 pounds of muscle easy. You cannot get nice muscles without doing carbs periods and I want to make a bet that if you do this Mark:

    – 1ste week 40gr. carbs before 1 hour workout (I do oat & buckwheat with whey in shake)

    – 2de week 80 grams

    – 3de week 120

    – 4de week 160

    – 5de week 200

    – 6de week 160

    – 7de week 120

    -8de week 80

    – 9de week 40

    En then of carbs for 3-6 months and look than to your muscles Mark. Much better!!! Carbs are not bad but you do need to have the right ones and not all the time but in cures. Good luck